To use the Remember The Milk API you need to have an application key; we use this to track API usage.

Non-commercial use

Your application is non-commercial if:

There is no plan to generate revenue (either directly or indirectly) from your project.

Please keep in mind that if you start with non-commercial use, and later decide to generate revenue with your project, there is absolutely no guarantee you'll be granted commercial use of the API in the future. You should be prepared to stick with non-commercial use if you choose this option!